It is troublesome to constantly maintain ordinary household knives, as well as other knives, in a sharpened condition due to the variations in actual time of usage of the knife. The user does not always remember when the blade should be sharpened until the knife is so dull that it will not cut. Often, it is not convenient to hone or otherwise sharpen the knife blade before each use and, over time, the cutting edge becomes dull, thus rendering the knife difficult to use. Furthermore, the extent to which the knife should be resharpened depends directly upon the dullness of the knife, with duller knives requiring a considerable amount of metal removal to produce a precise, sharp cutting edge.
A number of patent disclosures have recognized this deficiency with such ordinary knives, and provide a housing for receiving, protecting and sharpening or otherwise conditioning the cutting edge of a knife blade as the blade is inserted into or withdrawn from the housing. Typical patents in this area include U.S. Pat. Nos. 2,413,169; 2,475,937; 2,744,320; 2,767,530; 2,826,879; 3,676,961; 3,774,350; 3,861,246; 3,889,809; 4,041,651; 4,091,691 and 4,117,748. Each of these patents describes a device which is designed to sharpen the knife blade upon its insertion into and/or withdrawal from the housing. Each of these patents, with the exception of the '879 patent, include means, such as a spring, a latch member or a resilient member, for biasing the knife blade toward the sharpening elements. The device described in the '879 patent conditions a knife blade by burnishing it with abrasive cushions.
It has now been realized that these devices are deficient because they sharpen the blade upon each insertion and/or removal from the device, whether or not the blade requires sharpening. The sharpening action causes metal to be removed from the blade each time the knife is placed in and out of the scabbard or housing. Most of the time, after a single use of the knife, it is not necessary to sharpen the blade. Hence, these devices provide an unnecessary sharpening which causes the eventual wearing away of the blade.
Another knife sharpener is described in U.S. Pat. No. 4,494,339. This device is similar to those described in the patents mentioned above in that a spring is used to bias the knife blade edge against the sharpener; however, an adjustment knob is provided to vary the spring force and the extent of sharpening of the blade. This spring force may, if desired, be set to zero so as to render the sharpener ineffective.
The device described in the '339 patent is still deficient, however, in that the user of the knife must set the spring force each time the knife is inserted or withdrawn. As a practical matter, most users will set the adjustment at an intermediate position so that, in effect, the device performs the same as those discussed above.
In addition, many of the patents noted above fail to provide a device which can easily be stored on a flat surface, such as a countertop, to provide facilitated access to the user and which can accommodate a plurality of knives varying in size and shape.
U.S. Pat. Nos. 4,117,748 and 4,604,836 each describe a device which functions as a knife holder and sharpener which overcomes some of the deficiencies of the devices described in the aforementioned patents. For instance, U.S. Pat. No. 4,117,748 describes a knife scabbard and sharpening device having a support block and two sharpening plates secured thereto. The two sharpening plates are arranged in opposed and overlapping relationship to define a sharpening recess therebetween. However, in this device, the support block is pivotably mounted on a carrier to provide a rocking movement to the block and sharpening plates to achieve a properly honed knife edge. In addition, the user must vary the approach angle of the blade to distribute the wear over the greater part of each plate to prolong the effective life of the device.
U.S. Pat. No. 4,604,836 describes a safety cutlery case having a sharpening device which sharpens knives when they are driven into or removed from the case. This device also includes a sharpening means which is pivotably mounted within the case. The pivoted movement is necessary to reduce the resistance to the blade and to provide sufficient abrasion against the blade while not damping the movement of the knife. This device also requires a pressing member to retain the knife in engagement with the sharpening means, as is typical of most known devices.
The present invention provides a solution to those problems associated with the known devices in a convenient block having at least one housing member which both holds, protects, and, only when desired, simply and easily sharpens the blade of the knife to the desired extent. Use of the present device avoids the continuous wearing of the blade, yet provides a sharpening device which is readily available for use at the desire of the user, and in which the amount of force used to sharpen the knife blade, if any, is imparted by the user. Furthermore, since the present device does not have to be removed from its usual place of storage to permit a user to gain access to the knife or knives, the convenience of the present device offers an added improvement over the known devices. In addition, the structural arrangement of the sharpening element employed in the device of the present invention enables the user to achieve a perfectly honed blade edge without having to vary the approach angle of the blade, with minimal, if any, resistance to the blade.